The invention relates to a resistance material comprising a mixture of permanent and temporary binders and a metal rhodate resistance-determining component. The invention also relates to a resistor having a resistor body provided with leads, the resistor body having been produced by heating a substrate bearing such a resistance material so as to remove the temporary binder.
U.K. Pat. No. 1,535,139 (U.S. Pat. No. 4,107,387) describes such a resistance material in which the resistance-determining component is a metal rhodate having a composition defined by the formula M.sub.3 'Rh.sub.7 O.sub.15, M' preferably being Pb or Sr.
Compared to many oxidic compounds previously suggested for use as the resistance-determining compound in resistance materials, this compound has the advantage that it is a completed-reaction product which, with a permanent binder and, possibly, together with another resistance-determining component having a different temperature dependence of resistance, can be processed in a simple manner on a suitable substrate to form a resistor body. Prior to the development of these resistance materials, resistance pastes were available in which the resistance-determining component was not obtained until the paste had been fired on a substrate, a noble metal oxide reacting during the firing process with a vitreous binder, for example a lead oxide glass, which noble metal oxide and vitreous binder were present in the paste. This required a rather long firing time (for example half an hour) at a relatively high temperature (approximately 800.degree. C.).
A further advantage of the above-mentioned M.sub.3 'Rh.sub.7 O.sub.15 materials is the small negative temperature coefficient of resistance (TCR) of these materials, which temperature behavior is rare. Combining one of these materials with a material having a linear, positive temperature coefficient of resistance (which materials are much commoner than negative TCR materials) makes it possible to produce resistors having a very low TCR (/TCR/&lt;100.times.10.sup.-6 /.degree.C.) in a temperature range from -100- to +200.degree. C.